Most coals and petroleum contain large quantities of sulfur which form corrosive air and water pollutant products during combusion. Chemical and physical processes have been developed and are capable of removing inorganic sulfur contaminants such as sulfates and iron pyrites. A number of chemical processes for removal or organic sulfur are under investigation. Some of the processes being evaluated on a laboratory or pilot scale are oxydesulfurization, chlorinolysis, oxidation, hydrodesulfurization and gravimelt. According to Berry, (Berry, R. I. (1981)), "Guide to Coal Cleaning Methods," Chemical Engineering, Jan. 26, projected total product costs from bench and pilot scale operations ranged from $41 to $58 per ton (in 1979 U.S. dollars) for 10 to 50% organic sulfur removal.
Microbial treatment for removal of organic sulfur from coal may have important advantages. High temperatures, high pressures and corrosion resistant equipment are required for the chemical processes currently being evaluated. Microbial processes do not require high temperatures, high pressure or corrosion resistant equipment and, generally, inexpensive construction materials can be used resulting in low capital costs. Processing costs can also be low if waste materials and or inexpensive nutrient sources are used to support microbial growth. Ambient conditions may be used for biological treatment in many locales. In addition, microbial treatment will probably not significantly alter the coal structure or composition except for the sulfur removal, and will not substantially reduce the caloric content of the coal.
Experimental investigations for microbial treatment of petroleum and coal have used a variety of microorganisms, including genera such as Pseudomonas, Alcaligenes, Bacillus, Desulfovibrio, Thiobacillus, Arthrobacter, Flavobacterium, Beijerinckia, Rhizobium, Acinetobacter and Sulfolobus. Some of these microorganisms may have potential for degrading refractory organic sulfur compounds as discussed by Hedrick et al, (Hedrick, et al., 1982), "Desulfurization of Coal by Biological Pretreatment," State-of-the-art. A comprehensive summary of the experimental work in this area is presented in this report. Neither this report nor other available art discloses the mutant microorganisms Acinetobacter species CB2 (ATCC #53515) or its efficacy in removing organic sulfur from such as the aromatic sulfides found in carbonaceous materials.
An especially advantageous Pseudomonas species known as CB1 is described in U.S. Pat. No. 4,562,156 issued on the Dec. 31, 1985.
Although CB1 activity oxidizes certain types of organic sulfur, it does not have sufficient activity for oxidation of certain other types of organic sulfur.